Localized redistribution layer structure for embedded component package and method

ABSTRACT

An embedded component package includes an embedded component substrate. The embedded component substrate includes an electronic component having an active surface including bond pads and a package body encapsulating the electronic component. The package body includes a principle surface coplanar with the active surface, A localized redistribution layer (RDL) dielectric layer is on the active surface. A localized RDL conductive layer is on the localized RDL dielectric layer and is coupled to the bond pads through openings in localized RDL dielectric layer. A primary RDL dielectric layer encloses the entire embedded component substrate and directly contacts the localized RDL dielectric layer, the localized RDL conductive layer, and the principal surface of the package body. The localized RDL conductive layer provides additional space for routing of additional interconnects while the localized RDL dielectric layer acts as a stress buffer.

This application is a divisional application of a U.S. patentapplication entitled “LOCALIZED REDISTRIBUTION LAYER STRUCTURE FOREMBEDDED COMPONENT PACKAGE AND METHOD”, having a serial number of Ser.No. 14/860,426, having a filing date of Sep. 21, 2015, having commoninventors, and having a common assignee, all of which is incorporated byreference in its entirety.

FIELD

This disclosure relates generally to electronic component packages, andmore specifically, to embedded component packages and methods associatedtherewith.

BACKGROUND

Fan Out Wafer Level Packaging (FOWLP) is a wafer-level packagingtechnique which allows the production of an embedded component packagehaving multiple dies and passive components. The technique provides apackage with a reduced footprint and an increased area for solder ballconnection.

The embedded component package is formed by placing one or moreelectronic components, e.g., active components and passive components,onto an adhesive carrier with the electronic component terminals, e.g.,bond pads, facing the carrier. The electronic components are thenovermolded with a dielectric material, e.g., epoxy mold compound, toform an embedded component substrate. The embedded component substrateis a composite of the electronic components embedded within thedielectric material. The embedded component substrate is removed fromthe carrier.

To allow electrical interconnection with the embedded electroniccomponents, a dielectric layer is blanket formed across the entireembedded component substrate and covers the embedded electroniccomponents. Openings are formed in the dielectric layer to expose theterminals of the embedded electronic components. A metal layer is formedon the dielectric layer and extends through the openings to definecircuitry to redistribute the pattern of terminals of the embeddedelectronic components. The process of forming dielectric layers andmetal layers, sometimes called redistribution layer (RDL) dielectriclayers and RDL metal layers, is repeated depending upon theredistribution desired.

To smooth the unevenness of the embedded component substrate, thethickness of the RDL dielectric layer applied to the embedded componentsubstrate is relatively thick. The large thickness of the RDL dielectriclayer prevents formation of high aspect ratio openings within the RDLdielectric layer and fine pitch RDL metal layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of an embedded component package fabricationmethod in accordance with one embodiment.

FIG. 2 is a cross-sectional view of an embedded component package duringfabrication in accordance with one embodiment.

FIGS. 3, 4, 5, 6, 7, 8, 9, and 10 are cross-sectional views of theembedded component package of FIG. 2 at further stages duringfabrication in accordance with various embodiments.

The present invention is illustrated by way of example and is notlimited by the accompanying figures, in which like references indicatesimilar elements. Elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale.

DETAILED DESCRIPTION

An embedded component package includes a localized redistribution layer(RDL) dielectric layer and a localized RDL conductive layer formed atselect locations post panelization, i.e., after electronic componentsare encapsulated in a package body. The localized RDL dielectric layeris relatively thin and photo-definable. This allows small diameteropenings to be formed in the localized RDL dielectric layer and for thelocalized RDL conductive layer to be fine pitched.

Now in more detail, FIG. 1 is a flow diagram of an embedded componentpackage fabrication method 100 in accordance with one embodiment. FIG. 2is a cross-sectional view of an embedded component package 200 duringfabrication in accordance with one embodiment. In one embodiment,embedded component package 200 is a System in Package (SiP).

Referring now to FIGS. 1 and 2 together, an embedded component substrate202 is formed (102). More particularly, to form embedded componentsubstrate 202, one or more electronic components 204, 206, 208 aremounted to a carrier 210, e.g., an adhesive carrier.

In one embodiment, electronic components 204, 208 are active components,e.g., integrated circuit dies such as field-programmable gate arrayintegrated circuit dies. Electronic component 204 includes an active,e.g., first, surface 212 having bond pads 214 thereon. Electroniccomponent 204 further includes an inactive, e.g., second, surface 216opposite active surface 212.

Similarly, electronic component 208 includes an active, e.g., first,surface 218 having bond pads 220 thereon. Electronic component 208further includes an inactive, e.g., second, surface 222 opposite activesurface 218. Bond pads 214, 220 form the input/output (I/O) terminals ofelectronic components 204, 208. Active surfaces 212, 218 are mounted tocarrier 210.

In one embodiment, electronic component 206 is a passive component,e.g., a capacitor, resistor, or inductor. Electronic component 206including terminals 224 thereof is mounted to carrier 210.

Although examples of electronic components 204, 206, 208 are set forth,in other embodiments, embedded component substrate 202 is formed withadditional and/or different electronic components depending upon theparticular application.

After mounting of electronic components 204, 206, 208 to carrier 210,electronic components 204, 206, 208 are encapsulated in a dielectricpackage body 226, e.g., epoxy molding compound. Package body 226completely encloses electronic components 204, 206, 208 including theexposed portion of carrier 210. In one embodiment, package body 226 isback grinded to expose one or more of inactive surface 216, inactivesurface 222, or electronic component 206 as indicated by the dashed line227 of FIG. 2.

After formation of package body 226, package body 226 provides strengthand rigidity to embedded component substrate 202 allowing embeddedcomponent substrate 202 to be removed from carrier 210. Package body 226has a principle surface 226P parallel to and coplanar with activesurfaces 212, 218.

FIG. 3 is a cross-sectional view of embedded component package 200 ofFIG. 2 at a further stage during fabrication in accordance with oneembodiment. Note that in FIG. 3, embedded component substrate 202 isinverted from the view of FIG. 2.

Referring now to FIGS. 1 and 3 together, a next stage in processing isto form a localized redistribution layer (RDL) dielectric layer 328(104).

More particularly, localized RDL dielectric layer 328 is formedselectively, i.e., at selective locations and not blanket formed acrossthe entire embedded component substrate 202. In accordance with thisembodiment, localized RDL dielectric layer 328 is formed only onelectronic components 204, 208. For example, a dielectric layer isformed and then photo defined to form localized RDL dielectric layer328.

In one embodiment, electronic component 208 is relatively large, e.g.,active surface 218 of electronic component 208 is larger than activesurface 212 of electronic component 204. Localized RDL dielectric layer328 is formed on and covers the entire active surface 218 of electroniccomponent 208.

For example, due to the relatively large size of electronic component208, electronic component 208 is an area of high stress within embeddedcomponent package 200. The area of high stress is due to differentialthermal expansion of electronic component 208 relative to conductive(metal) layers to be formed on electronic component 208. Localized RDLdielectric layer 328 is a photo-definable low modulus, high elongationdielectric material that acts as a stress buffer on electronic component208. Low modulus of elasticity is desired when flexibility is needed;high elongation is the material's ability to stretch before breaking.Combined these properties tend to allow localized RDL dielectric layer328 to absorb more energy before it breaks.

By acting as a stress buffer, localized RDL dielectric layer 328minimizes the possibility of formation of cracks or other defects in theoverlying dielectric layers and conductive layers thus improvingreliability of embedded component package 200. Generally, localized RDLdielectric layer 328 as a photo-definable low modulus, high elongationdielectric material can be formed selectively in any high stress area,e.g., over large dies, stacked vias, filled vias, at surface mountcontact areas, or other desired locations.

Further, localized RDL dielectric layer 328 is formed on only a firstportion 329 of active surface 212 of electronic component 204 whileleaving a second portion 331 exposed. Localized RDL dielectric layer 328does not cover and is spaced apart from one or more of bond pads 214 onsecond portion 331, e.g., the bond pads 214A at the right edge ofelectronic component 204 in the view of FIG. 3. Localized RDL dielectriclayer 328 is not formed in direct contact with package body 226 in thisembodiment although extends onto principal surface 226P of package body226 in another embodiment.

Openings 330, sometimes called via openings 330, are formed in localizedRDL dielectric layer 328 extending to and exposing bond pads 214, 220 ofelectronic components 204, 208. Localized RDL dielectric layer 328 isrelatively thin and photo-definable. This allows small diameter openings330 to be formed to expose fine pitch bond pads 214, 220 individually.By exposing bond pads 214, 220 individually through openings 330,reliability is improved compared to forming a long trench to exposeseveral of bond pads 214, 220 collectively within a trench. However, inanother embodiment, openings 330 are trenches that expose a plurality ofbond pads 214, 220 collectively.

FIG. 4 is a cross-sectional view of embedded component package 200 ofFIG. 3 at a further stage during fabrication in accordance with oneembodiment. In FIG. 4, a first localized RDL conductive layer 432 isformed (106). For example, an electrically conductive material, e.g.,metal including copper, is deposited and then etched to form localizedRDL conductive layer 432. In another embodiment, electrically conductivematerial is selectively deposited, e.g., using a mask, to form localizedRDL conductive layer 432.

Localized RDL conductive layer 432 is formed on localized RDL dielectriclayer 328 and extends through, e.g., fills or lines, openings 330. Moreparticularly, localized RDL conductive layer 432 includes electricallyconductive vias 434 within openings 330 and electrically connected tobond pads 214, 220 of electronic components 204, 208. Further, localizedRDL conductive layer 432 includes electrically conductive traces 436 onlocalized RDL dielectric layer 328 and extending lengthwise in adirection parallel to active surfaces 212, 218. Traces 436 areelectrically connected to vias 434. Bond pads 214A remain exposed.

In one embodiment, traces 436 include lands 438 for electricalconnection to additional conductive layers as discussed further below.Traces 436 fan in the pattern of bond pads 214, 220 to the pattern oflands 438.

For example, bond pads 214, 220 are fine pitched bond pads adjacent theouter periphery of active surfaces 212, 218 designed for wire bonding.Traces 436 fan in the pattern of bond pads 214, 220 from the outerperiphery of active surfaces 212, 218 to the pattern of lands 438distributed, e.g., as an array, on active surfaces 212, 218. The pitchbetween lands 438 is greater than the fine pitch of band pads 214, 220.This provides additional space for routing additional interconnects asset forth below. Generally, localized RDL conductive layer 432 enablesescape routing far multiple contact arrays.

Also, as illustrated by the center bond pad 220 of electronic component208, in one embodiment, lands 438 are also formed directly upon vias434.

Localized RDL conductive layer 432 is formed on electronic components204, 208 post panelization, i.e., after electronic components 204, 208are encapsulated in package body 226. This avoids performing theredistribution on electronic components 204, 208 while still in waferform allowing electronic components 204, 208 to be sourced from multiplemanufactures, e.g., OEMs.

Although vias 434 are illustrated in FIG. 4 as solid vias completelyfilling openings 330, in another embodiment, vias 434 are hollow viasthat line the sidewall of openings 330 while leaving an empty spaceinside of vias 434 and openings 330. This empty space is subsequentlyfilled with an overlying layer. Generally, filled vias are illustratedherein in the various figures. However, in other embodiments, instead offilled vias, hollow vias are formed and the empty space within thehollow vias is subsequently filled with an overlying layer.

FIG. 5 is a cross-sectional view of embedded component package 200 ofFIG. 4 at a further stage during fabrication in accordance with oneembodiment. In FIG. 5, a first primary RDL dielectric layer 540 isformed (108).

Primary RDL dielectric layer 540 is blanket formed across the entireembedded component substrate 202. Primary RDL dielectric layer 540completely covers the underlying structure and directly contactslocalized RDL conductive layer 432, localized RDL dielectric layer 328,principle surface 226P of package body 226, and the exposed secondportion 331 of electronic component 204.

In accordance with this embodiment, openings 542 are formed in primaryRDL dielectric layer 540. Openings 542 expose lands 438 of localized RDLconductive layer 432, terminals 224 of electronic component 206, and thebond pads 214A of electronic component 208 that are uncovered by andexposed from localized RDL dielectric layer 328.

FIG. 6 is a cross-sectional view of embedded component package 200 ofFIG. 5 at a further stage during fabrication in accordance with oneembodiment. In FIG. 6, a primary RDL conductive layer 644 is formed(110). For example, an electrically conductive material is deposited andthen etched to form primary RDL conductive layer 644. In anotherembodiment, electrically conductive material is selectively deposited,e.g., using a mask, to form primary RDL conductive layer 644.

Primary RDL conductive layer 644 is formed on primary RDL dielectriclayer 540 and extends through, e.g., fills or lines, openings 542. Moreparticularly, primary RDL conductive layer 644 includes electricallyconductive vias 646 within openings 542. Vias 646 are electricallyconnected to lands 438 of localized RDL conductive layer 432, terminals224 of electronic component 206, and bond pads 214A of electroniccomponent 204 that are exposed from localized RDL dielectric layer 328.

Further, primary RDL conductive layer 644 includes electricallyconductive traces 648 on primary RDL dielectric layer 540 and extendinglengthwise in a direction parallel to active surfaces 212, 218. Traces648 are electrically connected to vias 646.

In one embodiment, traces 648 include lands 650 for electricalconnection to additional conductive layers as discussed further below.Traces 648 redistribute the pattern of lands 438, terminals 224, andbond pads 214A to the pattern of lands 650.

In one embodiment, one or more electronic components 652 are located onprimary RDL dielectric layer 540. Illustratively, primary RDL conductivelayer 644 itself is patterned into electronic component 652, e.g., an RFcoil or antenna. However, in another embodiment, electronic component652 is a separate structure mounted to primary RDL dielectric layer 540and connected to primary RDL conductive layer 644.

Also, as illustrated above the center bond pad 220 of electroniccomponent 208, in one embodiment, vias 646 are also formed directly uponvias 434 to form a stacked via 654. Stacked via 654 is used due torouting constraints for example. Localized RDL dielectric layer 328 onelectronic component 208 operates as a stress buffer around stacked via654.

As illustrated in FIG. 6, localized RDL conductive layer 432 is embeddedwithin primary RDL dielectric layer 540. Localized RDL conductive layer432 provides embedded localized smaller scale redistribution withinprimary RDL dielectric layer 540.

In one embodiment, localized RDL dielectric layer 328 is thinner thanprimary RDL dielectric layer 540. The thickness is measured in adirection perpendicular to active surfaces 212, 218. For example, thethickness of localized RDL dielectric layer 328 is within the range of 2μm to 5 μm and the thickness of primary RDL dielectric layer 540 iswithin the range of 14 μm to 20 μm. Due to the reduced thickness oflocalized RDL dielectric layer 328, the diameter of openings 330 can bemade smaller than the diameter of openings 542. Stated another way,small discrete openings 330 can be formed to expose fine pitch bond pads214, 220.

Further, in one embodiment, localized RDL dielectric layer 328 is madeof a material different than the material of primary RDL dielectriclayer 540. For example, primary RDL dielectric layer 540 is epoxy,polyimide, benzocyclobutene (BCB), or polybenzoxazole (PBO). Examples oflocalized RDL dielectric layer 328 include polyimide, benzocyclobutene(BCB), polybenzoxazole (PBO), fluorinated polymer, or siloxane. Althoughvarious examples of dielectric materials for localized RDL dielectriclayer 328 and primary RDL dielectric layer 540 are given, in otherembodiments, other dielectric materials are used. Further, in oneembodiment, the same dielectric material is used for both localized RDLdielectric layer 328 and primary RDL dielectric layer 540.

Further, in one embodiment, localized RDL conductive layer 432 isthinner than primary RDL conductive layer 644. For example, thethickness of localized RDL conductive layer 432 is 2 μm and thethickness of primary RDL conductive layer 644 is within the range of 4μm to 10 μm. Due to the reduced thickness of localized RDL conductivelayer 432, the feature size, e.g., the width and/or spacing betweentraces 436, of localized RDL conductive layer 432 can be made smallerthan the feature size of primary RDL conductive layer 644. Due to thesmall feature size of localized RDL conductive layer 432, fine pitchfeatures, e.g., bond pads 214, 220, can be readily redistributedallowing further integration and density of routing. Localized RDLconductive layer 432 is sometimes called a small form factor RDL.

FIG. 7 is a cross-sectional view of embedded component package 200 ofFIG. 6 at a further stage during fabrication in accordance with oneembodiment. In FIG. 7, a second localized RDL dielectric layer 756 isformed (112).

More particularly, localized RDL dielectric layer 756 is formedselectively, i.e., at selective locations and not blanket formed. Inaccordance with this embodiment, localized RDL dielectric layer 756 isformed only on electronic component 652, e.g., a RF coil or antenna. Inone embodiment, localized RDL dielectric layer 756 is a low loss tangentdielectric material providing excellent insulation of electroniccomponent 652 from conductive layers to be formed thereon as discussedfurther below. Low loss tangent'low dissipation factor dielectricmaterials are important when signal distortion must be minimized, andwhen signal integrity (SI) must be preserved. Loss tangent ordissipation factor is a measure of a dielectric material's tendency toabsorb some of the energy from an electromagnetic (EM) field passingthrough the material. More particularly, using a low loss tangentdielectric material as localized RDL dielectric layer 756 allows otherconductive layers to be formed on top of electronic component 652reducing the size (footprint) of embedded component package 200.

In accordance with this embodiment, one or more openings 758, sometimescalled via openings 758, are formed in localized RDL dielectric layer756 to expose terminal(s) 760 of electronic component 652. However, inanother embodiment, localized RDL dielectric layer 756 is formed withoutopenings 758 and completely covers and electrically insulates electroniccomponent 652.

FIG. 8 is a cross-sectional view of embedded component package 200 ofFIG. 7 at a further stage during fabrication in accordance with oneembodiment. In FIG. 8, a localized RDL conductive layer 862 is formed(114) in a manner similar to that discussed above regarding localizedRDL conductive layer 432 and so is only briefly discussed below.

Localized RDL conductive layer 862 is formed on localized RDL dielectriclayer 756 and fills or lines openings 758. More particularly, localizedRDL conductive layer 862 includes electrically conductive vias 864within openings 758 and electrically connected to terminals 760 ofelectronic component 652. Further, localized RDL conductive layer 862includes electrically conductive traces 866 on localized RDL dielectriclayer 756 and extending lengthwise in a direction parallel to activesurfaces 212, 218. Traces 866 are electrically connected to vias 864.

In one embodiment, traces 866 include lands 868 for electricalconnection to additional conductive layers as discussed further below,Traces 866 redistribute the pattern of terminals 760 to the pattern oflands 868. This allows for added complexity and functionality whilereducing the size (footprint) of embedded component package 200.However, in another embodiment, e.g., when openings 758 are not formedin localized RDL dielectric layer 756, operation 114 is not performedand thus localized RDL conductive layer 862 is not formed.

FIG. 9 is a cross-sectional view of embedded component package 200 ofFIG. 8 at a further stage during fabrication in accordance with oneembodiment. In FIG. 9, a second primary RDL dielectric layer 970 isformed (116).

Primary RDL dielectric layer 970 is similar to and formed in a similarmanner as primary RDL dielectric layer 540 discussed above and so isonly briefly discussed below. Primary RDL dielectric layer 970 isblanket formed and includes openings 972. Openings 972 expose lands 650and lands 868.

Further, in FIG. 9, a second primary RDL conductive layer 974 is formed(118). Primary RDL conductive layer 974 is similar to and formed in asimilar manner as primary RDL conductive layer 644 discussed above andso is only briefly discussed below.

Primary RDL conductive layer 974 is formed on primary RDL dielectriclayer 970 and fills or lines openings 972. More particularly, primaryRDL conductive layer 974 includes electrically conductive vias 976within openings 972. Vias 976 are electrically connected to lands 650,868. Further, primary RDL conductive layer 974 includes electricallyconductive traces 978 on primary RDL dielectric layer 970 and extendinglengthwise in a direction parallel to active surfaces 212, 218. Traces978 are electrically connected to vias 976.

In one embodiment, traces 978 include lands 980 for electricalconnection to additional conductive layers as discussed further below.Traces 978 redistribute the pattern of lands 650, 868 to the pattern oflands 980. Form additional primary RDL dielectric layer operation 116and form additional primary RDL conductive layer operation 118 arerepeated as many times as necessary until the desired redistribution isachieved.

FIG. 10 is a cross-sectional view of embedded component package 200 ofFIG. 9 at a further stage during fabrication in accordance with oneembodiment. In FIG. 10, an outer dielectric layer 1082 is formed (120).

Outer dielectric layer 1082 is similar to and formed in a similar manneras primary RDL dielectric layer 970 discussed above and so is onlybriefly discussed below.

Outer dielectric layer 1082 is blanket formed and includes land openings1084, Land openings 1084 expose lands 980. Outer dielectric layer 1082is the outermost dielectric layer in accordance with this embodiment andelectrically isolates principle RDL conductive layer 974 from theambient environment.

Further, in FIG. 10, an interconnection structure 1086 is formed withinland openings 1084 and on lands 980 (122). In one embodiment,interconnection structure 1086 includes a plurality of electricallyconductive bumps, e.g., forming a ball grid array. Interconnectionstructure 1086 provides the structure for interconnection of embeddedcomponent package 200 with other structures, e.g., a printed circuitboard.

In one embodiment, a plurality of embedded component packages 200 areformed simultaneously in an array. In accordance with this embodiment,the array is singulated to form a plurality of individual embeddedcomponent packages 200.

Although the invention is described herein with references to specificembodiments, various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. Any benefits, advantages, or solutions to problemsthat are described herein with regard to specific embodiments are notintended to be construed as a critical, required, or essential featureor element of any or all the claims.

Unless stated otherwise, terms such as “first” and “second” are used toarbitrarily distinguish between the elements such terms describe. Thus,these terms are not necessarily intended to indicate temporal or otherprioritization of such elements.

What is claimed is:
 1. A method comprising: forming a first primaryredistribution layer (RDL) dielectric layer on an embedded componentsubstrate; forming a first primary RDL conductive layer on the firstprimary RDL dielectric layer; forming a localized RDL dielectric layeron the first primary RDL conductive layer; and forming a second primaryRDL dielectric layer directly contacting the first primary RDLdielectric layer, the first primary RDL conductive layer, and thelocalized RDL dielectric layer.
 2. The method of claim 1 wherein thefirst primary RDL conductive layer comprises an electronic component,the localized RDL dielectric layer covering the electronic component. 3.The method of claim 2 wherein the electronic component is selected fromthe group consisting of an antenna and a coil.
 4. The method of claim 2wherein the localized RDL dielectric layer comprises a low loss tangentdielectric material.
 5. The method of claim 2 wherein the localized RDLdielectric layer completely covers the electric component.
 6. The methodof claim 2 further comprising: forming a localized RDL conductive layeron the localized RDL dielectric layer.
 7. The method of claim 6 whereinthe localized RDL conductive layer includes an electrically conductivevia electrically coupled to a terminal of the electronic component. 8.The method of claim 6 wherein the second primary RDL dielectric layerdirectly contacts the localized RDL conductive layer.
 9. The method ofclaim 6 wherein the localized RDL conductive layer includes conductivetraces extending lengthwise in a direction parallel to a major surfaceof the embedded component substrate.
 10. The method of claim 6 whereinthe localized RDL conductive layer is coupled to the electroniccomponent through an opening in the localized RDL dielectric layer. 11.The method of claim 6 wherein a thickness of the localized RDLconductive layer is less than a thickness of the first primary RDLconductive layer.
 12. The method of claim 1 further comprising: mountingan electronic component to the primary RDL dielectric layer.
 13. Themethod of claim 12 wherein the localized RDL dielectric layer covers theelectronic component.
 14. The method of claim 12 wherein the electroniccomponent is selected from the group consisting of an antenna and acoil.
 15. The method of claim 12 wherein the localized RDL dielectriclayer comprises a low loss tangent dielectric material.
 16. The methodof claim 12 wherein the localized RDL dielectric layer completely coversthe electric component.
 17. The method of claim 1 further comprising:forming a localized RDL conductive layer on the localized RDL dielectriclayer.
 18. The method of claim 17 wherein the second primary RDLdielectric layer directly contacts the localized RDL conductive layer.19. The method of claim 17 wherein the localized RDL conductive layerincludes conductive traces extending lengthwise in a direction parallelto a major surface of the embedded component substrate.
 20. The methodof claim 17 wherein the localized RDL conductive layer is coupled to theelectronic component through an opening in the localized RDL dielectriclayer.